Periodic behaviour of coronal mass ejections, eruptive events, and solar activity proxies during solar cycles 23 and 24

We report on the parallel analysis of the periodic behaviour of coronal mass ejections (CMEs) based on 21 years [1996 -- 2016] of observations with the SOHO/LASCO--C2 coronagraph, solar flares, prominences, and several proxies of solar activity. We consider values of the rates globally and whenever possible, distinguish solar hemispheres and solar cycles 23 and 24. Periodicities are investigated using both frequency (periodogram) and time-frequency (wavelet) analysis. We find that these different processes, in addition to following the $\approx$11-year Solar Cycle, exhibit diverse statistically significant oscillations with properties common to all solar, coronal, and heliospheric processes: variable periodicity, intermittence, asymmetric development in the northern and southern solar hemispheres, and largest amplitudes during the maximum phase of solar cycles, being more pronounced during solar cycle 23 than the weaker cycle 24. However, our analysis reveals an extremely complex and diverse situation. For instance, there exists very limited commonality for periods of less than one year. The few exceptions are the periods of 3.1--3.2 months found in the global occurrence rates of CMEs and in the sunspot area (SSA) and those of 5.9--6.1 months found in the northern hemisphere. Mid-range periods of $\approx$1 and $\approx$2 years are more wide spread among the studied processes, but exhibit a very distinct behaviour with the first one being present only in the northern hemisphere and the second one only in the southern hemisphere. These periodic behaviours likely results from the complexity of the underlying physical processes, prominently the emergence of magnetic flux.Comment: 33 pages, 15 figures, 2 table

Time-Dependent Tomographic Reconstruction of the Solar Corona

Solar rotational tomography (SRT) applied to white-light coronal images observed at multiple aspect angles has been the preferred approach for determining the three-dimensional (3D) electron density structure of the solar corona. However, it is seriously hampered by the restrictive assumption that the corona is time-invariant which introduces significant errors in the reconstruction. We first explore several methods to mitigate the temporal variation of the corona by decoupling the "fast-varying" inner corona from the "slow-moving" outer corona using multiple masking (either by juxtaposition or recursive combination) and radial weighting. Weighting with a radial exponential profile provides some improvement over a classical reconstruction but only beyond 3 Rsun. We next consider a full time-dependent tomographic reconstruction involving spatio-temporal regularization and further introduce a co-rotating regularization aimed at preventing concentration of reconstructed density in the plane of the sky. Crucial to testing our procedure and properly tuning the regularization parameters is the introduction of a time-dependent MHD model of the corona based on observed magnetograms to build a time-series of synthetic images of the corona. Our procedure, which successfully reproduces the time-varying model corona, is finally applied to a set of of 53 LASCO-C2 pB images roughly evenly spaced in time from 15 to 29 March 2009. Our procedure paves the way to a time-dependent tomographic reconstruction of the coronal electron density to the whole set of LASCO-C2 images presently spanning 20 years.Comment: 24 pages, 18 figure

Alzheimer’s Disease Computer-Aided Diagnosis on Positron Emission Tomography Brain Images Using Image Processing Techniques

Positron emission tomography (PET) is a molecular medical imaging modality which is commonly used for neurodegenerative disease diagnosis. Computer-aided diagnosis (CAD), based on medical image analysis, could help with the quantitative evaluation of brain diseases such as Alzheimer’s disease (AD). Ranking the effectiveness of brain volume of interest (VOI) to separate healthy or normal control (HC or NC) from AD brain PET images is presented in this book chapter. Brain images are first mapped into anatomical VOIs using an atlas. Different features including statistical, graph, or connectivity-based features are then computed on these VOIs. Top-ranked VOIs are then input into a support vector machine (SVM) classifier. The developed methods are evaluated on a local database image as well as on Alzheimer’s Disease Neuroimaging Initiative (ADNI) public database and then compared to known selection feature methods. These new approaches outperformed classification results in the case of a two-group separation

Stimulated Raman histology: one to one comparison with standard hematoxylin and eosin staining

International audienceWe present for the first time one-to-one correspondence between standard hema-toxylin/eosin (H&E) stained tissue sections and stimulated Raman histology (SRH)-a label-free technique in which stimulated Raman scattering (SRS) and second harmonic generation (SHG) are combined to generate virtual H&E images. Experiments were performed on both human thin cryogenic slides from the gastrointestinal tract (GI) and thick freshly excised biopsies from endoscopic surgery. Results on cryogenic slides evidenced an excellent agreement between SRH and H&E images while the ones on biopsies established the relevance of SRH for rapid intraoperative histology to assist in surgical decision making

Analyse d'images multi-modales TEP-TDM du thorax. Application à l'oncologie : segmentation de tumeurs, d'organes à risque et suivi longitudinal pour la radiothérapie

In oncological thoracic imaging, computerized tomography (CT) and positron emission tomography (PET) are widely used jointly, for diagnosis or treatment planing. The development of combined scanners enables the acquisition of pairs of CT-PET volumes, allowing their joint exploitation in clinical routine, without the prerequisite for complex registration. One goal of this thesis work was to propose a segmentation method jointly exploiting PET and CT image information. The proposed methodology therefore focuses on a detailed segmentation of the CT images, using PET information to guide the tumor segmentation. The framework of variational segmentation methods is used to design our algorithms and the specific constraints based on PET information. In addition to target structures for radiotherapy (tumors, nodules), organs at risk which need to be preserved from radiations, must be segmented. An additional goal of this thesis is to provide segmentation methods for these organs. The methods rely on strong a priori knowledge on the non-parametric intensity distributions and on the shapes of the different organs. A final goal of the thesis is to propose a methodological framework for the segmentation of tumors in the context of longitudinal follow up of patients with registered images. The proposed segmentation methods were tested on multiple data sets. When manual tracing is available, quantitive comparisons of the segmentations are presented, demonstrating the performance and accuracy of the proposed segmentation framework.En oncologie du thorax, les modalités d'imagerie de tomodensitométrie (TDM) et d'imagerie d'émission de positons (TEP) sont souvent utilisées conjointement, pour le diagnostic ou pour l'élaboration de plans de traitement. En effet, le développement d'appareils d'acquisition combinant ces deux modalités permet leur utilisation conjointe possible en routine clinique sans une difficulté préalable de recalage. Le premier objectif est de proposer des méthodes de segmentation automatiques de tumeurs ou ganglions à l'aide des deux modalités. La modalité TDM étant anatomiquement plus précise les segmentation sont réalisées dans cette modalité en utilisant l'imagerie TEP comme guide pour la localisation de la tumeur. Les organes à risque, devant être protégés des irradiations, nécessitent aussi d'être contourés. Un autre objectif est de proposer des algorithmes permettant leur segmentation. Ils s'appuient sur une connaissance a priori forte des distributions d'intensités des différents organes dans les images TDM et de connaissances a priori de formes des organes à segmenter. Un dernier objectif est de proposer une méthodologie pour la segmentation de tumeurs dans le cadre du suivi longitudinal des patients dans des images préalablement recalées. L'ensemble des méthodes de segmentation a été testé sur différents jeux de données, et lorsque des segmentations manuelles expertes sont disponibles, des résultats quantitatifs sont présentés, montrant l'intérêt des approches proposées et la précision des résultats obtenus

Connecting Coronal 3D Electron Density from Tomographic Reconstruction to In-situ Measurements from Parker Solar Probe

International audienceThere are few possibilities to put the in-situ measurements of the coronal electron density such as obtained by the Parker Solar Probe (PSP) in the context of the 3D configuration of the corona and its structure. One of them consists in using MHD models relying on synoptic maps of the photospheric magnetic field, but their accuracy is subject to questions, especially in the case of complex coronae of the maximum type. The 2D inversion of white-light coronagraphic images requires the simplified assumption of spherical symmetry of the corona which basically washes out the longitudinal variations. We will present preliminary results of a new method which makes use of the 3D time-dependent tomographic reconstruction of the coronal electron density based on accurately corrected and calibrated LASCO-C2 images of the polarized brightness of the corona. It is performed over a sliding window of 14 days (half a Carrington rotation) centered at the times of the PSP perihelion with a time interval of 4 days. The resulting “cubes” of the 3D electron density Ne are visualized from six different vantage points and with movies. The orbit of PSP is projected on a synoptic map of Ne extracted from the cubes at a heliocentric distance of 5.5 Rs; the track extends from Perihelion-5 days to Perihelion+5 days. The electron density at the heliocentric distances of PSP is extrapolated radially from the values at 5.5 Rs using an inverse square law and compared with the in-situ measurements collected by PSP/FIELDS. We will present results from the first ten PSP encounters

Connecting Coronal 3D Electron Density from Tomographic Reconstruction to In-situ Measurements from Parker Solar Probe

International audienceThere are few possibilities to put the in-situ measurements of the coronal electron density such as obtained by the Parker Solar Probe (PSP) in the context of the 3D configuration of the corona and its structure. One of them consists in using MHD models relying on synoptic maps of the photospheric magnetic field, but their accuracy is subject to questions, especially in the case of complex coronae of the maximum type. The 2D inversion of white-light coronagraphic images requires the simplified assumption of spherical symmetry of the corona which basically washes out the longitudinal variations. We will present preliminary results of a new method which makes use of the 3D time-dependent tomographic reconstruction of the coronal electron density based on accurately corrected and calibrated LASCO-C2 images of the polarized brightness of the corona. It is performed over a sliding window of 14 days (half a Carrington rotation) centered at the times of the PSP perihelion with a time interval of 4 days. The resulting “cubes” of the 3D electron density Ne are visualized from six different vantage points and with movies. The orbit of PSP is projected on a synoptic map of Ne extracted from the cubes at a heliocentric distance of 5.5 Rs; the track extends from Perihelion-5 days to Perihelion+5 days. The electron density at the heliocentric distances of PSP is extrapolated radially from the values at 5.5 Rs using an inverse square law and compared with the in-situ measurements collected by PSP/FIELDS. We will present results from the first ten PSP encounters

Connecting Coronal 3D Electron Density from Tomographic Reconstruction to In-situ Measurements from Parker Solar Probe

International audienceThere are few possibilities to put the in-situ measurements of the coronal electron density such as obtained by the Parker Solar Probe (PSP) in the context of the 3D configuration of the corona and its structure. One of them consists in using MHD models relying on synoptic maps of the photospheric magnetic field, but their accuracy is subject to questions, especially in the case of complex coronae of the maximum type. The 2D inversion of white-light coronagraphic images requires the simplified assumption of spherical symmetry of the corona which basically washes out the longitudinal variations. We will present preliminary results of a new method which makes use of the 3D time-dependent tomographic reconstruction of the coronal electron density based on accurately corrected and calibrated LASCO-C2 images of the polarized brightness of the corona. It is performed over a sliding window of 14 days (half a Carrington rotation) centered at the times of the PSP perihelion with a time interval of 4 days. The resulting “cubes” of the 3D electron density Ne are visualized from six different vantage points and with movies. The orbit of PSP is projected on a synoptic map of Ne extracted from the cubes at a heliocentric distance of 5.5 Rs; the track extends from Perihelion-5 days to Perihelion+5 days. The electron density at the heliocentric distances of PSP is extrapolated radially from the values at 5.5 Rs using an inverse square law and compared with the in-situ measurements collected by PSP/FIELDS. We will present results from the first ten PSP encounters

Analyse d'images multimodales TEP-TDM du thorax (Application à l'oncologie)

En oncologie du thorax, les modalités d'imagerie de tomodensitométrie (TDM) et d'imagerie d'émission de positons (TEP) sont souvent utilisées conjointement, pour le diagnostic ou pour l'élaboration de plans de traitement. En effet, le développement d'appareils d'acquisition combinant ces deux modalités permet leur utilisation conjointe possible en routine clinique sans une difficulté préalable de recalage.Le premier objectif est de proposer des méthodes de segmentation automatiques de tumeurs ou ganglions à l'aide des deux modalités. La modalité TDM étant anatomiquement plus précise les segmentation sont réalisées dans cette modalité en utilisant l'imagerie TEP comme guide pour la localisation de la tumeur. Les organes à risque, devant être protégés des irradiations, nécessitent aussi d'être contourés. Un autre objectif est de proposer des algorithmes permettant leur segmentation. Ils s'appuient sur une connaissance a priori forte des distributions d'intensités des différents organes dans les images TDM et de connaissances a priori de formes des organes à segmenter. Un dernier objectif est de proposer une méthodologie pour la segmentation de tumeurs dans le cadre du suivi longitudinal des patients dans des images préalablement recalées. L'ensemble des méthodes de segmentation a été testé sur différents jeux de données, et lorsque des segmentations manuelles expertes sont disponibles, des résultats quantitatifs sont présentés, montrant l'intérêt des approches proposées et la précision des résultats obtenus.In oncological thoracic imaging, computerized tomography (CT) and positron emission tomography (PET) are widely used jointly, for diagnosis or treatment planing. The development of combined scanners enables the acquisition of pairs of CT-PET volumes, allowing their joint exploitation in clinical routine, without the prerequisite for complex registration. One goal of this thesis work was to propose a segmentation method jointly exploiting PET and CT image information. The proposed methodology therefore focuses on a detailed segmentation of the CT images, using PET information to guide the tumor segmentation. The framework of variational segmentation methods is used to design our algorithms and the specific constraints based on PET information. In addition to target structures for radiotherapy (tumors, nodules), organs at risk which need to be preserved from radiations, must be segmented. An additional goal of this thesis is to provide segmentation methods for these organs. The methods rely on strong a priori knowledge on the non-parametric intensity distributions and on the shapes of the different organs. A final goal of the thesis is to propose a methodological framework for the segmentation of tumors in the context of longitudinal follow up of patients with registered images. The proposed segmentation methods were tested on multiple data sets. When manual tracing is available, quantitive comparisons of the segmentations are presented, demonstrating the performance and accuracy of the proposed segmentation framework.PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF